1. Field of the Invention
The present invention relates to a vehicle steering device in which both the front wheels and the rear wheels are steered.
2. Description of the Prior Art
In the past, four-wheeled vehicles, such as automobiles and trucks, have conventionally been steered by manipulation of the front wheels only. Front wheel steering has proved to be satisfactory for operation of most vehicles, particularly smaller wheelbase vehicles such as automobiles. Steering of both the front and rear wheels has not been considered particularly useful for most straight ahead driving situations.
However, it would be desirable in longer wheelbase vehicles, such as large vans, to steer the rear wheels under certain conditions. For example, if the rear wheels can be steered when turning around a corner, making a U-turn, and other similar situations, the turning radius is desirably reduced to facilitate improved maneuverability of such vehicles in situations where turning space is limited.
In accordance with the present invention, a rear wheel steering drive mechanism is provided wherein the steering action for the rear wheels does not come into play until after the front wheels have been turned through a preliminary angle. The rear wheels are only steered after the front wheels have been turned beyond an angle which represents a severe turn of the vehicle such as will occur when making a U-turn or going around a corner. In straight ahead driving, the rear wheels are not steered during small steering manipulations of the front wheels which normally occur during the course of such straight ahead driving. U.S. Pat. No. 4,813,694, issued Mar. 21, 1989, illustrates a cam actuated mechanism suitable for this purpose. The present invention relates to a simplified cam operated mechanism.